A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth. Then, (a) the linear momentum of S remains constant in magnitude. (b) the acceleration of S is always directed towards the centre of the earth. (c) the angular momentum of S about the centre of the earth changes in direction, but its magnitude remains constant. (d) the total mechanical energy of S varies periodically with time.

Answer: (b). Gravity on S always points to the Earth's centre (central force), so the acceleration is always towards the centre. (a) Wrong: speed changes along an ellipse, so momentum magnitude changes. (c) Wrong: central force gives zero torque, so angular momentum is constant in both magnitude and direction. (d) Wrong: only gravity acts, so total mechanical energy is constant. So the answer is (b).

A satellite S is moving in an elliptical orbit around the earth. The… | NEET 2015 (AIPMT)

Q25NEET 2015 · AIPMTMedium

Kepler's Laws & Planetary Motion

A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth. Then,

Show answer and solution

Answer: (b)

Gravity on S always points to the Earth's centre (central force), so the acceleration is always towards the centre.
(a) Wrong: speed changes along an ellipse, so momentum magnitude changes.
(c) Wrong: central force gives zero torque, so angular momentum is constant in both magnitude and direction.
(d) Wrong: only gravity acts, so total mechanical energy is constant.
So the answer is (b).

Report a mistake

Kepler's Laws & Planetary Motion question from NEET 2015 (AIPMT)

More questions on Kepler's Laws & Planetary Motion